This invention relates in general to certain new and useful improvements in a system for programmably digitizing a control apparatus, and more particularly, to a system for programmably digitizing a control apparatus which provides control operation over a composite-tape placement machine.
In recent years, reinforced plastic composite materials have achieved increased prominence and have been used in the manufacture of a variety of products which are normally formed of heavy metals and other counterpart structural materials. For example, motor casings, rotor blades, tubular members such as pipes, and various other types of structural members which were formerly fabricated from various metals, are now being constructed with reinforced plastics. These reinforced plastic composite materials normally employ fiber reinforcement such as fiberglass or boron fibers in a curable resin matrix.
Many of the structural members used in the air frame industry are presently formed of aluminum and other lightweight metals. However, there has also been a recent transition to the employment of reinforced plastics in the production of the structural members. Conventional filament winding systems have been employed in the fabrication of these reinforced plastic components, but these conventional filament winding systems suffer from a number of serious drawbacks. In order to increase productivity in the manufacture of these components, resort has been made to the use of tape application or so-called "tape laying" equipment.
However, the extant tape laying equipment is ineffective in many cases because the filament reinforced tapes must be applied to a work surface in a very precise manner and within fairly close tolerance limitations.
Applying a wide filament reinforced composite tape to conform to compound curved surfaces presents a substantial problem in the presently available tape placement devices, inasmuch as it may be necessary to compensate for the bending of the tape in a span-wise direction. Accordingly, the existant tape placement heads are not capable of laying a fairly wide tape on a compound curved surface in a fair and tight manner under proper control. Furthermore, problems of unequal demand distribution across the tape's width resulting from proportional difference in elemental geodesic path lengths often arise. This unequal demand distribution will vary according to the degree of curvature and this may range from fractional amounts to very substantial dimensional differences.
Among the other problems encountered in the use of the conventional presently available tape laying machine resides in the failure of the tape laying head to properly sever the tape at a desired location, and at a pre-selected angle with respect to the work surface. Furthermore, the tape must be dispensed or unspooled under careful control and this control is difficult to maintain due to the modulus of induced rigidity in the tape. Thus, considerable problems are encountered in maintaining proper tension on the tape as it is applied to the work surface due to the fact that the convolute windings of the tape tend to expand and unwind in the manner of a released clock spring.
These problems mentioned above often require the construction of a rather complex tape placement head which must include components necessary to perform all of the required functions. In addition, the gantry machine which holds the tape placement head must be controlled in some fashion so that all functions to be performed by the tape placement head can be precisely performed in a proper time sequence. In many cases individual controls are provided for each function which require manual activation by an operator. As can be expected, manual control by an operator has proven to be relatively ineffective.
There have been several attempts to use various forms of external control apparatus, such as numeric control apparatus. However, these forms of apparatus must be properly programmed in order to control the gantry machine and the tape placement head. Thus, the numeric control apparatus must be programmed to enable the tape placement head to move in precise directions in any of a number of axes, and perhaps in several of the axes at the same time. For example, the tape placement head may be required to simultaneously shift vertically as well as transversely and longitudinally in order to cover a particular portion of a tape receiving surface. In addition, the control apparatus must be properly programmed to enable the tape placement head to compensate for variations of compound curvature on the work surface. Even more-so, the numeric control system must be properly programmed in order to timely initiate tape severing functions and the like.
In order to properly program the numeric control apparatus, very extensive programs are required which may often take several man years or more of time in order to generate the necessary program. Even more-so, the program must be revised each time that the tape size is changed or the tape receiving surface is altered. Consequently, these disadvantages of numeric control systems have militated against their use and furthermore, have militated against the use of various forms of commercially available tape laying equipment.